1. Field of the Invention
The present invention relates to a sealing structure for sealing a gap between an outer peripheral member and an inner peripheral member which is installed to the outer peripheral member in an inserted state, and more particularly relates to a sealing structure preferably used for high-pressure gas sealing, for example, sealing a gap between an attaching hole which is provided in a cylinder head of an internal combustion engine, and a leading end portion of an injector, a combustion sensor or a cylinder internal pressure sensor which is installed to the attaching hole in an inserted state.
2. Description of the Conventional Art
An in-cylinder direction injection type internal combustion engine is structured such as to directly inject fuel into a cylinder by an injector, and the injector is attached in an inserted state to an injector attaching hole which is provided in a cylinder head. Accordingly, in the injector, combustion gas is prevented from leaking by a seal ring so as to inhibit the combustion gas leakage from a gap between an inner peripheral surface of the injector attaching hole and an outer peripheral surface of the injector.
FIG. 7 shows a sealing structure between an injector attaching hole and an injector according to a prior art. More specifically, in FIG. 7, reference numeral 100 denotes a cylinder head of an internal combustion engine, and reference numeral 110 denotes an injector. The injector 110 is attached in an inserted state to an injector attaching hole 101 which is provided in the cylinder head 100 and is communicated with a combustion chamber (E), and is a device which directly injects fuel into the combustion chamber (E). A gap between the injector attaching hole 101 and a leading end portion of the injector 110 is sealed by a seal ring 120.
For details, on an outer peripheral surface in the vicinity of the leading end of the injector 110, there are formed a taper-like outer peripheral surface 111 which is smaller in its diameter toward an inserting direction thereof (a combustion chamber (E) side), an installation portion outer peripheral surface 112 which extends in the inserting direction from its small diameter end portion (a lower end), and a leading end outer peripheral surface 114 which is larger in its diameter than the installation portion outer peripheral surface 112 via a stepped surface 113 rising up in a diametrical direction from an end portion in the inserting direction in the installation portion outer peripheral surface 112. Further, the seal ring 120 standing between the injector attaching hole 101 and the leading end portion of the injector 110 is made of a synthetic resin material, for example, poly tetra fluoro ethylene (PTFE) having a high heat resistance, and is formed approximately into a rectangular shape in its cross sectional shape which is cut by a plane passing through a center axis, an outer peripheral surface 120a of the seal ring is brought into close contact with an inner surface of the injector attaching hole 101, and an inner peripheral surface 120b of the seal ring is brought into close contact with the installation portion outer peripheral surface 112 of the injector 110.
Therefore, according to the sealing structure, the seal ring 120 approximately having the rectangular shape in its cross sectional shape runs on the taper-like outer peripheral surface 111 from the installation portion outer peripheral surface 112 of the injector 110 while being displaced to an atmospheric air side space (A) side by pressure P of combustion gas in the combustion chamber (E) side, and is compressed in a diametrical direction between the inner peripheral surface of the injector attaching hole 101 and the taper-like outer peripheral surface 111 as shown in FIG. 8, and close contact surface pressure is increased by reaction force of the compression, so that it is possible to effectively shut off the combustion gas (refer, for example, to Japanese Patent No. 4342121 and Japanese Patent No. 3830896).